Like multi-air-conditioning apparatuses for use in building, some air-conditioning apparatuses each include heat source unit (outdoor unit) disposed outside a building and an indoor unit disposed in a room of the building. Refrigerant circulating through a refrigerant circuit of such an air-conditioning apparatus rejects heat into (or removes heat from) air that is supplied to a heat exchanger of the indoor unit and thereby heats or cools the air. Then, the air thus heated or cooled is sent into an air-conditioned space so that heating or cooling is performed.
Adopted examples of heat source side refrigerants that are used in such air-conditioning apparatuses include many types of HFC (hydrofluorocarbon) refrigerant. Further, an example of heat source side refrigerant involves the use of a natural refrigerant such as carbon dioxide (CO2).
Further, there have been proposed various types of air-conditioning apparatus each including, as heat source unit disposed outside a building, a chiller that generates cooling energy or heating energy (see, for example, Patent Literature 1). Patent Literature 1 discloses a technology with which to perform heating or cooling by heating or cooling a heat medium such as water or antifreeze with an intermediate heat exchanger disposed in the chiller and conveying the heat medium via heat medium pipes to a fan coil unit, a panel heater, or a similar device serving as an indoor unit (see, for example, Patent Literature 1).
Further, there has been proposed an air-conditioning apparatus, called an exhaust heat recovery chiller, having four heat medium pipes connected between heat source unit and an indoor unit (see, for example, Patent Literature 2). Patent Literature 2 discloses a technology with which to supply a heated heat medium and a cooled heat medium to the indoor unit simultaneously and allow a free choice of cooling or heating at the indoor unit.
Further, there has been proposed an air-conditioning apparatus including a primary side refrigerant circuit through which a primary refrigerant circulates and a secondary side refrigerant circuit through which a secondary refrigerant circulates, the secondary refrigerant serving as a heat medium, the secondary side refrigerant circuit including a use-side heat exchanger, wherein an intermediate heat exchanger that exchanges heat between the primary refrigerant and the secondary refrigerant is disposed near each indoor unit (see, for example, Patent Literature 3).
Further, there has been proposed an air-conditioning apparatus configured such that a heat source side refrigerant heated or cooled by an outdoor unit is supplied to an intermediate heat exchanger mounted in a branch unit and the heating energy or cooling energy of the heat source side refrigerant thus supplied is transferred to a heat medium via the intermediate heat exchanger (see, for example, Patent Literature 4). Patent Literature 4 discloses a technology with which an indoor unit and the branch unit are connected to each other by two heat medium pipes.
Further, there has been proposed an air-conditioning apparatus, such as a multi-air-conditioning apparatus for use in building, in which to, by circulating refrigerant from an outdoor unit to a relay unit and circulating a heat medium such as water from the relay unit to an indoor unit, circulate the heat medium such as water through the indoor unit and, at the same time, allow the heat medium to be conveyed with less power (see, for example, Patent Literature 5).